1. Field of the Invention
The present invention relates to thermostats. More specifically, the present invention is directed to a thermostat having heat anticipation.
2. Description of the Prior Art
A conventional thermostat utilizes a temperature responsive element, e.g., a bimetallic strip, to produce a mechanical motion as a function of the ambient or environmental temperature being monitored by the thermostat. The temperature responsive element is used to operate an electrical switch element for controlling a heat source affecting the monitored ambient temperature. It is desirable in such a thermostat application to maintain a minimum temperature differential, i.e., temperature variation, in the area being heated. To this end, so-called heat anticipation thermostats have been developed. Such a thermostat provides a control of the heat source prior to the attainment of a desired temperature in the area being heated, i.e., the thermostat anticipates the attainment of the temperature. In a heat anticipation control system, the heat source is turned off before the ambient temperature of the area reaches the desired temperature to avoid an overshoot or temperature increase past the desired temperature. Such an anticipation action is needed as a result of a time lag in heat transmission from the source to the area being heated which would normally produce a temperature increase in the area being heated for a period of time after the heat source is turned off. Conventional heat anticipation thermostats have used an auxiliary heat source, e.g., an electrical resistance heater, for artificially providing a heating operation of the heat sensing element as an anticipation operation, e.g., the thermostat shown in U.S. Pat. No. 3,339,043. While such a heater element does effect an anticipation operation for a thermostat, it also is a separate element which increases the price and complexity of the thermostat. Accordingly, it would be desirable to provide a heat anticipation thermostat having inherent heating capability for heat anticipation without the need for a separate heating element.